Battery technology is a great candidate for energy storage applications. The need for high-performance and cost-effective batteries has motivated researchers to put much effort into improving battery performance. In this work, we attempt to understand the elements that affect the microstructure and performance of two battery systems. The first part of this work focuses on the investigation of transport and structural properties of porous electrodes in an alkaline electrolyte. A DC polarization method was deployed for tortuosity measurements. An apparatus was designed to flow specified current through and measure the voltage drop over the porous electrodes. Using a modified Ohm's law, effective diffusion coefficient and associated tortuosity were determined. Multiple compositions (different types and amounts of conductive additives) were tested to understand the effects of composition on the transport properties. As a validation and to further understand the tests, a model was developed and used for data analysis. The second part of this dissertation describes simulations of the manufacturing process of a Li-ion electrode. LAMMPS, a particle simulator, was used for this meso-scale particle-based simulation. The interactions between particles were understood by model-experiment comparisons of the macroscopic properties such as viscosity of the slurry and elasticity of the dried film. The microstructure created by this simulation was consistent with the one we observed in SEM/ FIB images. Although the emphasis was the drying process in this part, some preliminary coating and calendering simulations are presented. Finally, the effects of electrode heterogeneity were investigated by a Newman-type model and tomographic images. An electronic conductivity map was initially generated over a Li-ion cathode. Then SEM/FIB images of specified high, middle, and low conductivity regions were taken to confirm heterogeneity. For modeling purposes, three regions of high, middle, and low ionic resistance were considered connected in parallel, representing the real electrode heterogeneity. Multiple cases of heterogeneities such as non-uniform ionic resistance and active material loading at low, middle, and high charge-discharge rates were studied. The results show that higher rates increase non-uniformities of dependent properties such as temperature, current density, positive and negative electrodes states of charge, and charge and discharge capacities especially in charging cases.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-7791 |
| Date | 01 April 2018 |
| Creators | Forouzan, Mohammad Mehdi |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Theses and Dissertations |
| Rights | http://lib.byu.edu/about/copyright/ |
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